Bannon, who in August declared, "The Trump presidency that we fought for, and won, is over," after he left his White House job, told people in private that he was disappointed in Trump's chaotic leadership style, according to the article.

Bannon also told a friend in November that he believes his former boss has since "lost a step."

"He's like an 11-year-old child," Bannon joked, according to Vanity Fair.

Bannon didn't have nice things to say about Trump's children, either. On Ivanka, Trump's elder daughter, Bannon called her a "fount of bad advice during the campaign."

The article doesn't just highlight the fraying relationship between Trump and his former chief strategist but also raises questions about Bannon's own political ambitions.

The article contends that starting with a call to an adviser in October, Bannon has considered running for president if Trump does not run for re-election in 2020. Bannon says privately that he gives Trump only about a 30% chance of lasting through his first presidential term, the article reported.

A source who works for Bannon told CNN, "Steve Bannon is 100% not running for president."

Bannon appeared to concede that it's likely his campaign would not ultimately succeed, telling Vanity Fair, "I'm not a political operative," but instead, "I'm a revolutionary."